尿素是固态氮肥,肥效高,呈中性,不破坏土壤结构。尿素属有机态氮肥,作物不能直接吸收,在土壤中经尿素酶分解,变成碳酸铵才能被作物吸收利用。碳酸铵稳定性差,易逐渐分解成氨气逸失;同时尿素态氮不易被土壤颗粒吸附,在没有转化之前,易随水流失。目前常用的撒施利用率一般只有33％,研究合理施用尿素,提高尿素肥效对促进农作物的增产有积极作用。作者在1976年研究的基础上,于1977年又对不同茬口水稻进行尿素肥效试验,结果:1.尿素的肥效与施肥深度关系极大。其肥效随深度增加,稻谷、稻草产量均增加;根重也有增加趋势;其肥力消长趋势是深层施> Urea is a solid nitrogen fertilizer, high efficiency, was neutral, does not destroy the soil structure. Urea is an organic nitrogen fertilizer, crops can not be directly absorbed in the soil by urease decomposition, into ammonium carbonate to be absorbed by crops. The stability of ammonium carbonate is poor, easy to gradually decompose into ammonia escape; the same time, urea nitrogen is not easily adsorbed by soil particles, without conversion, easy to drain with water. At present, the commonly used rate of spreading is only 33%. Researching the rational application of urea and improving the urea efficiency have a positive effect on increasing crop yield. On the basis of the study of 1976, the author conducted urea fertilization experiment on different stubble rice in 1977, and the results were as follows: 1. The effect of urea on fertilization depth was greatly related to the depth of fertilization. The fertilizer efficiency increased with depth, rice and straw production increased; root weight also increased; the trend of its decline and fertilization is deep application>